Studies of metallic thin film growth in an atomic layer epitaxy reactor using M(acac)2 (M = Ni, Cu, Pt) precursors

Feasibility of metallic thin film growth by atomic layer epitaxy (ALE) was studied in the case of divalent metal beta-diketonate-type precursor M(acac)(2) (M = Ni, Cu and Pt) at 250 degrees C and 1 mbar. Metallic films were obtained by two different approaches: (i) direct layer-by-layer reduction of the adsorbed precursor by H-2, and (ii) by first depositing a metal oxide thin film by ALE and then converting it to the metallic form by a separate reduction step. The latter case was demonstrated by converting a NiO thin film, deposited at 250 degrees C on glass substrate with O-3 as an oxygen source, to metallic Ni at 260 degrees C and 1 atm by 5% H-2. AFM study indicated, however, pinhole formation and, thus, deformation of the initial dense structure of NiO. In the case of direct layer-by-layer reduction by H-2, attention was focused on the effects of the substrate on the film growth by applying Ti, Al, Si(100) and glass substrates. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) studies indicated that metallic Ni, Cu and Pt film growth proceeded preferably on Ti and Al substrates. On Si substrate, the film growth was restricted by interdiffusion and silicide formation; whereas on the glass substrate, the dim growth was related to the gas phase stability of the precursors and proceeded mainly by pyrolysis. (C) 2000 Elsevier Science B.V. All rights reserved.